Field of the Invention
The invention relates to polyhydroxyamides that can be used for preparing highly crosslinked polymers and to temperature stable polymers prepared from these polyhydroxyamides. The invention further relates to polymers that have been three-dimensionally crosslinked using the polyhydroxyamides.
In microelectronics, in the automobile industry, in mechanical engineering, and in the aerospace industry, chemically-inert, high-heat-resistance polymers are needed as protective and insulating coats. In microelectronics, such polymers are used, for example, as a dielectric between the chip and a metallization level or between two metal levels in a chip: for example, in multichip modules or in memory chips and logic chips. Furthermore, such polymers are also used as a buffer coat between chip and housing. In the automobile industry, in mechanical engineering, and in the aerospace industry, such chemically-inert, high-heat-resistance polymers are needed for producing weather-resistant protective coats.
Polybenzoxazoles exhibit a high level of temperature stability and great chemical resistance. They are generally prepared from polyhydroxyamides that are readily soluble in organic solvents, such as N-methyl-pyrrolidone. The solutions can be applied to surfaces by spin coating, by dipping or by brush methods. The solvent can be removed subsequently by heating, which can be accompanied or followed by cyclization of the polyhydroxyamide to the polybenzoxazole, with elimination of water, in accordance with the reaction depicted below, so giving a polymer having the properties described above. 
Polyhydroxyamides that are readily soluble in organic solventsand exhibit good temperature stability are described, for example, in European Patent Application No. EP 0 317 942 (which corresponds to U.S. Pat. No. 4,845,183), European Patent No. EP 0 512 339 B1 (which corresponds to U.S. Pat. No. 5,376,499), German published, non-prosecuted Application No. DE 37 17 212 A1, or U.S. Pat. No. 5,077,378 issued to Mueller et al. These materials, however, exhibit only moderate adhesion to substrates such as, for example, silicon oxide, silicon nitride, titanium nitride, tantalum nitride, glass or metals.
U.S. Pat. No. 3,644,288 issued to Odier et al. describes three-dimensionally crosslinked polybenzoxazoles obtained by cyclization from the corresponding crosslinked hydroxypolyamides by heating to a temperature in the range 220-400xc2x0 C. The hydroxypolyamides are obtained by reacting an aromatic dihydroxydiamine compound, a dicarboxylic acid compound, and a tricarboxylic acid compound with one another. In one variant, the hydroxypolyamides are prepared by preparing in a first stage a linear polyamide of low molecular weight, starting from a dihydroxydiamine and a dicarboxylic acid compound, and in a second stage crosslinking this linear polyamide by adding a triester of a tricarboxylic acid. The hydroxypolyamides obtained in this way have a structure that is three-dimensionally crosslinked to a high degree and are therefore insoluble solids. For further processing, these solids are pulverized. Accordingly, it is very difficult if not impossible to process these hydroxypolyamides to thin coats, because they cannot be applied to a surface by spin coating in the form of a solution in an appropriate solvent, These hydroxypolyamides are therefore unsuited to application in microelectronics.
U.S. Pat. No. 3,644,286 issued to Odier et al. describes crosslinked polyamides and processes for preparing them. Appropriate dihydroxydiamines are reacted with dicarboxylic acid derivatives and tricarboxylic acid derivatives to give infusible solids that cannot be dissolved in organic solvents and sulphuric acid. Since these polyhydroxyamides cannot be applied in the form of a thin coat to a substrate, these compounds are likewise unsuited to application in microelectronics.
It is accordingly an object of the invention to provide a material and additive for highly crosslinked chemically and thermally stable polyhydroxyamide polymers that overcome the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and that are readily soluble in organic solvents and, from which, it is possible to prepare polybenzoxazoles that have good insulating properties, high thermal and chemical stability, and good adhesion to all customary substrates.
This object is achieved by a polyhydroxyamide of the Formula I 
where
a, axe2x80x2, axe2x80x3 to d, dxe2x80x2, dxe2x80x3 may each be identical or different and
a=0 or 1;
b=0 to 100;
c=0 or 1; and
d=0 or 1;
where
if a=0, b=c=0;
if c=0, d=0;
if d=1, e=1; and
if a =1 and b=c=0, d=0; and
where
Z1, Z2, and Z3, which may each be identical or different, denote a tetravalent radical having up to 100 carbon atoms;
Y1, Y2, and Y3, which may each be identical or different, denote a divalent radical containing at least two carbonyl groups which form an amide bond to the adjacent nitrogen, and comprising up to 100 carbon atoms; and
X, independently at each occurrence, denotes hydrogen or a monovalent radical having up to 30 carbon atoms which comprises at least one reactive group which is able to form a bond to another reaction center.
The polyhydroxyamides of the invention are readily soluble in many organic solvents, such as cyclohexanone, diethylene glycol monoethyl or diethyl ether, N-methylpyrrolidone, xcex3-butryolactone or ethyl lactate. They can be processed readily, for example, by spin coating or by brush methods. After drying and baking on the substrate, during which the polyhydroxyamide is cyclized to the polyoxazole, the resulting film exhibits a substantially higher thermal stability than other comparable materials and a markedly better adhesion to a variety of substrates.
The polyhydroxyamides of the invention include as their central unit a radical derived from the benzenetricarboxylic acid. Going out from this central unit in a star formation are three linear side chains. In this form, the polyhydroxyamide of the Formula I does not yet exhibit a highly crosslinked form. However, because the side chains carry terminal groups X that can react with further compounds, the polyhydroxyamides of the Formula I are able to react with further polymers and crosslink them. Therefore, by adding polyhydroxyamides of the Formula I, highly-three-dimensionally crosslinked structures that possess high mechanical stability can be formed. By adding reactive groups X, containing for example a polymerizable double bond, the polyhydroxyamides of the Formula I may also be crosslinked further themselves. Accordingly, the polyhydroxyamides of the Formula I, accordingly can also be used themselves as a starting product for conversion into corresponding polybenzoxazoles. As a result of the branching of the polymers at the central unit derived from a benzenetricarboxylic acid, and/or, where appropriate, by further crosslinking, the polymer acquires a desirable high mechanical stability. The polyhydroxyamides of the Formula I may also, however, be used as crosslinking agents for other, preferably linear, polymers. Through the fraction of the added polyhydroxyamides of the Formula I, it is possible in this case to control the degree of crosslinking and consequently, for example, the solubility of the crosslinked polymer in an organic solvent as well. The central radical is preferably of symmetrical construction; in other words, it is derived from 1,3,5-benzenetricarboxylic acid. However, other substitution patterns of the central benzene nucleus may be realized. Attached to each of the three carbonyl groups of the central benzene radical, via an amide bond, is a side chain. The three side chains may be identical or different and may have different chain lengths. The conditions stated for the indices a to d therefore apply analogously to the indices axe2x80x2 to dxe2x80x2 and, respectively, axe2x80x3 to dxe2x80x3 as well. Depending on the chosen conditions for the preparation of the polyhydroxyamides of the invention, it is also possible to obtain mixtures of polymers with different side chain lengths. Especially with increasing side chain lengths, these polymers, viewed macroscopically, exhibit a distribution in the length of the side chains. In that case, although the indices a to d, axe2x80x2 to dxe2x80x2, and axe2x80x3 to dxe2x80x3 still correspond to whole numbers for one individual molecule, viewed macroscopically the average is determined over all of the side chains. This relates in particular to the indices b, bxe2x80x2, and bxe2x80x3. The side chains each include groups Z1 to Z3, Y1 to Y3, and X. The groups Z1 to Z3, Y1 to Y3, and X may each be identical or different in the three side chains. Preferably, the three side chains each contain identical radicals Z1 to Z3, Y1 to Y3, and X, respectively. Further, these groups Z1 to Z3, Y1 to Y3, and X may exhibit a high degree of variability in their structure, in which case the properties of the polyhydroxyamide and, respectively, of the crosslinked polymer obtained from it can be modified further through the structure of these groups.
The groups Z1 to Z3 each form a tetravalent radical that may include up to 100 carbon atoms. The 4 bonds are each formed to a hydroxyl group or to the nitrogen of an amide bond. The hydroxyl groups and the nitrogens are each attached to a 5- or 6-membered aromatic or heteroaromatic radical, with one hydroxyl group and one nitrogen being arranged in each case vicinally on the aromatic or heteroaromatic radical. As a result, two pairs of substituents are formed on each of the groups Z1 to Z3, each pair being formed by a hydroxyl group and by an amide nitrogen disposed vicinally to it. The two pairs of substituents may be disposed on the same radical or else on different radicals within the respective groups Z1 to Z3. By cyclization with the carbonyl carbon of the amide bond, an oxazole structure may be formed from each of the pairs of substituents. As the aromatic radical to which in each case at least one substituent pair, including hydroxyl group and amide nitrogen, is attached within the groups Z1 to Z3, a phenyl ring is preferred. As the heteroaromatic radicals to which in each case at least one substituent pair, including hydroxyl group and amide nitrogen, is attached within the groups Z1 to Z3, both 5-membered and 6-membered rings are preferred, it is possible for these rings to include one or more heteroatoms. Preferred heteroatoms are oxygen, sulfur, and nitrogen atoms. The aromatic or heteroaromatic radicals may in each case carry further substituents, examples being alkyl groups, aryl groups, fused-on aromatic or heteroaromatic groups or else halogens or pseudohalogens. Where, within the groups Z1 to Z3, the substituent pairs formed from a hydroxyl group and an amide nitrogen are attached to different aromatic or heteroaromatic radicals, these radicals may be connected by fused-on phenyl radicals, by fused-on heteroaromatic 5- or 6-membered radicals or by cycloalkyl radicals, especially cyclohexyl and cyclopentyl radicals. Alternatively, the radicals that carry the substituent pairs may be connected by way of alkylene groups, preferably a methylene group. It is possible for these alkylene groups as well, which preferably comprise from 1 to 10 carbon atoms, to carry further substituents, examples being alkyl groups or halogen atoms, and to contain heteroatoms, such as nitrogen, sulfur or silicon, in the alkyl chain or pendantly. Interlinking by way of a single bond or a heteroatom, an ether group or a thioether group, for example, is also possible. The alkylene chain may further include double bonds and triple bonds as well.
Preferably, Z1 to Z3 are selected from the group including the following: 
where R2 stands for a divalent radical selected from the group including the following: 
where g denotes an integer between 1 and 10;
R4 denotes an alkyl group having 1 to 10 carbons, an aryl group having 6 to 20 carbons or an aralkyl group having 7 to 30 carbons, and
R5 denotes an alkylene group having 1 to 10 carbons, an arylene group having 6 to 20 carbons or an aralkylene group having 7 to 30 carbons.
The groups Y1 to Y3, as a repeating unit, produce the connection between two adjacent units each formed by the groups Z1 to Z3. The Y1 to Y3 group may also exhibit a very great structural diversity. The groups Y1 to Y3 each contain at least two carbonyl groups, which in each case together with the nitrogen attached to the adjacent Z1 to Z3 group form an amide bond. The carbonyl group is preferably attached to a phenyl ring, the two carbonyl groups being able to be attached to the same phenyl radical or to different phenyl radicals. Where the carbonyl groups are attached to different phenyl rings of the respective groups Y1 to Y3, the phenyl groups may be connected by way of a single bond or by way of an alkylene radical, preferably including 1 to 10 carbon atoms. The alkylene radical can contain heteroatoms, especially O, S and N, pendantly or in the chain, and to be substituted by further groups, especially fluorine. The phenyl rings that carry the carbonyl group may also be connected to one another by way of fused phenyl rings, or cycloalkyl groups may be formed between the phenyl rings. The phenyl groups may also carry one or more further substituents, examples being halogen, alkyl groups, alkenyl groups, alkynyl groups, alkoxy groups, alkenoxy groups or ester groups. The groups Y1 to Y3 may each also comprise heteroaromatic radicals, especially 5- and 6-membered rings that may contain one or more heteroatoms, especially O, S, and N.
Preferably, Y1 to Y3 is selected is from the following group: 
where
f denotes an integer between 1 and 10 or, if R2 is a single bond or *xe2x80x94CH2xe2x80x94*, denotes an integer between and including 0 and 10;
R1, independently at each occurrence, denotes at least one radical selected from the group 
R2 is as defined in claim 2; and
R3 is selected from the group including the following: 
where h denotes an integer between and including 0 and 10.
The group X from Formula I permits polymerization of the polyhydroxyamides of the invention and/or copolymerization with further monomers and/or crosslinking of polymers that contain a reactive group. The group X must therefore include at least one reactive group that is able to form a bond to a further reaction center. The reactive group is preferably a polymerizable double or triple bond.
Where the side chain ends with a radical formed by a Z1 to Z3 group, X at its most simple is a hydrogen atom. In that case the side chain ends with an amino group, which is then able to produce a bond to a further polymer, by nucleophilic attack on the carbon atom of a carbonyl or carboxyl group. Preferably, X includes a polymerizable double or triple bond by which attachment to the double or triple bond of a further polymer can take place, by way for example of a free radical reaction. Preferred radicals for the group X are depicted below, with a=b=c=0 or d=0 and X selected from the following group: 
Where the side chain ends with a Y1 to Y3 group, X may for example be a hydroxyl group. In that case, the side chain ends with a carboxyl group, which by way of an amide bond, for example, is able to react with the amino group of a further polymer. The terminal group Y1 to Y3 may also be in ester form. In that case the group X is, for example, an alkoxy group or alkenoxy group. Corresponding cycloalkyl groups or aromatic groups are also possible. The group X may also be in the form of an amino group. In that case the Y1 to Y3 group possesses a terminal acid amide group, it being possible for the nitrogen atom thereof to be substituted by an alkyl radical, alkenyl radical, cycloalkyl radical, aryl radical, or aralkyl radical.
Preferred radicals for the group X are set out below, with a=1 and b=c=d=0 or d=1 and X selected from the following group: 
As already stated above, polymers having advantageous properties may be obtained from the polyhydroxyamides described above. The invention therefore also provides a temperature stable polymer obtained by polymerizing the polyhydroxyamide described above. The polymerisation takes place preferably with heating, with ring closure to the oxazole being possible simultaneously or in a separate temperature step.
The polyhydroxyamide from which the temperature stable polymer is obtained preferably includes a group X containing at least one polymerizable double or triple bond.
However, the polyhydroxyamides of the invention may also be used for crosslinking other polymers. The crosslinking produces a polymer having improved mechanical and chemical stability. The invention therefore additionally provides a three-dimensionally crosslinked polymer obtained by subjecting a monomer, oligomer, or polymer containing at least one reactive group which is able to react with the group X of one of the above-described polyhydroxyamides to form a chemical bond to reaction with one of the above-described polyhydroxyamides.
The group X in this case preferably includes a polymerizable double or triple bond and the reactive group that is able to react with the group X of the polyhydroxyamide to form a chemical bond preferably includes a polymerizable double or triple bond.
The invention is illustrated below by examples. First of all, various polyhydroxyamides are prepared, and are then reacted to give polymers. After that, the properties of the polymers are investigated further.
In the synthesis of the polyhydroxyamides, the following compounds are used as starting materials. The abbreviations of the compounds are also used subsequently.
Bisaminophenol 1
9,9xe2x80x2-Bis(4-((3-hydroxy-4-amino)phenyloxy)phenyl)fluorine 
Bisaminophenol 2
2,2-Bis(3-amino-4-hydroxyphenyl)hexafluoropropane 
Bisaminophenol 3
3,3xe2x80x2-Diamino-4,4xe2x80x2-dihydroxybiphenyl 
Dicarbonyl Chloride 1
2,2-Bis(4-chlorocarbonylphenyl)hexafluoropropane 
Endcap 1
Phenylpropiolyl chloride 
Endcap 2
Methacryloyl chloride 
Endcap 3
5-Norbornene-2-carbonyl chloride 
Other features that are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is described herein as embodied in a material and additive for highly crosslinked chemically and thermally stable polyhydroxyamide polymers, it is, nevertheless, not intended to be limited to the exemplary details since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments and examples.